how would one go about creating an epic animated landscape?
To operate with high polycounts you should make sure that your scene preview subsurface levels are as low as possible when you aren't working on them(so split up your scene into smaller sections). Also, you can put sections you aren't working on in wireframe view(this does help). Splitting stuff up into different scenes also helps. 

When I do high polycount scenes I work on them section by section on different layers then put them all together but only leave the center in solid mode.

So yes, Blender can work with high polycounts on a lower machine but you'll probably have to jump through some hoops to do it.